towards a new french etrs89 realization for the rgp krgp...

EUREF Symposium – Brussels, June 18-21, 2008

Towards a new french ETRS89 realization for the RGP k iRGP network stations

Alain Harmel (IGN/SGN)( )Bruno Garayt (IGN/SGN)

Motivations

The aim of this work was not to change the french ETRS89 realization “RGF93” definition (at least in the near future) which has a l l t t b t tlegal status, but to propose:

• A monitoring process of the french GNSS permanentA monitoring process of the french GNSS permanent network (RGP)

• A cumulative solution expressed in IGS05 for velocity and• A cumulative solution expressed in IGS05 for velocity and coordinates estimation

• f f• A set of coordinates expressed in ETRF2000 for the stations of the RGP (called ETRF2000(R05)-F) and a grid model based on collocation method from/to the RGF93 reference frame

EUREF 2008, Brussels

Towards a new french ETRS89 realization based for the RGP network stations

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The network and the data included in the analysis

161161 stations from the IGS/EPN, EPN IGS/EPN, EPN and RGP and RGP networksnetworks

more than 2 years of data less than 2 years of data ITRF2005/IGS05 reference stations

GPS data only from GPS week 0938 to 1462



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The general processing strategy

Daily/weekly freefree solutions (SINEX) loosely constrained GPS processing : Bernese software 5.0Bernese software 5.0

y y ( ) y(1m)

Monitoring process using SGN combination programs and analysis tools

Final solution using CATREFCATREF package and the minimum constraint approach

analysis tools

- A cumulative IGS05 solution (positions and velocities) is processed. A SINEX file is produced.- Final coordinates are expressed in the IGS05 at 2008.0 reference epcoh.

approach

Final coordinates are expressed in the IGS05 at 2008.0 reference epcoh.

Velocities are constrainted to be the same within the same site

Conversion to ETRS89 using Approach A formulae to compute a set of coordinates for the RGP stations defining a french realization of the ETRS89 system



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The GPS processing strategy

The processing strategy adopted was those used at the IGN LAC. It is based on ionosphere-free double differences in a network approach using the Bernese 5.0 software and the following options/parameters:

• DE200 planetary ephemeris model• Earth potential model : JGM3• Ground/satellite antenna : IGS absolute/relative elevation-dependent phase center models

Measurement models

p p• Ocean loading model : FES2004• Solid Earth tides applied (IERS Conventions 2003)• Orbits and ERPs : IGS final products

Processing parametersProcessing parameters• Elevation dependant weighting• Elevation angle cutoff : 3 degrees• Troposphere :

mapping function : Wet Niellmapping function : Wet Niellzenith delays estimated once per hour for each stationdaily horizontal gradient parameters

Estimated parameters• Adjustment : Weighted least-squares algorithms• Ambiguity resolution : QIF strategy. Solved ambiguities introduced to final solution• Free solutions (loosely constrained) : the 7 daily solutions are combined to produce a weekly solution• Troposphere : zenith delays estimated once per hour for each station and daily horizontal gradient



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• Troposphere : zenith delays estimated once per hour for each station and daily horizontal gradient

Reference frame definition

Minimun constraints over a set of selected stations of the ITRF2005/IGS05 stations005/ GS05 s a o s

EUROPEAN IGS05 reference stations

+ S I T E / I D* C O D E P T _ _ D O M E S _ _ T _ S T A T I O N D E S C R I P B R U S A 1 3 1 0 1 M 0 0 4 B R U S S E L S , B E L G I U C A G L A 1 2 7 2 5 M 0 0 3 C a g l i a r i , I t a l y G R A S A 1 0 0 0 2 M 0 0 6 C A U S S O L S , F R A N C E H O F N A 1 0 2 0 4 M 0 0 2 H O F N 1 0 2 0 4 M 0 0 2 M A S 1 A 3 1 3 0 3 M 0 0 2 M A S P A L O M A S , S P A I M A T E A 1 2 7 3 4 M 0 0 8 M A T E R A , I T A L Y M E T S A 1 0 5 0 3 S 0 1 1 K I R K K O N U M M I ( 4 0 O N S A A 1 0 4 0 2 M 0 0 4 O N S A L A , S W E D E N P D E L A 3 1 9 0 6 M 0 0 4 P O N T A D E L G A D A , P P O T S A 1 4 1 0 6 M 0 0 3 P O T S D A M , G E R M A N Y S F E R A 1 3 4 0 2 M 0 0 4 S A N F E R N A N D O ( C A W S R T A 1 3 5 0 6 M 0 0 5 W E S T E R B O R K , N E T H

1 4 2 0 1 0 1 0 W T Z R A 1 4 2 0 1 M 0 1 0 K O E T Z T I N G , G E R M A Z I M M A 1 4 0 0 1 M 0 0 4 Z I M M E R W A L D , S W I T- S I T E / I D

IGS05 : more consistent with the use of the receiver Absolute Phaseof the receiver Absolute Phase Center Variation models (APCV)



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A monitoring approach (1/2)

To deal with discontinuities (antenna change / analysis) at reference epoch using IGS05 realization, the position differences from ITRF2005 h b i t d dhave been introduced.

A program has been developped to propagate coordinates at selected epoch using an extended CRD Bernese format

RGP IGS05 18-JUN-08 09:19RGP IGS05 18 JUN 08 09:19--------------------------------------------------------------------------------LOCAL GEODETIC DATUM: IGS05 EPOCH: 2008-01-01 00:00:00

NUM STATION NAME X (M) Y (M) Z (M) FLAG FROM TO

1 CO 13434 0011 4594489 6880 678367 7079 4357066 1692 99 237 00000 00 008 432001 ACOR 13434M0011 4594489.6880 -678367.7079 4357066.1692 E 99:237:00000 00:008:432002 ACOR 13434M0012 4594489.6824 -678367.7044 4357066.1735 E 00:008:43200 01:353:432003 ACOR 13434M0013 4594489.6791 -678367.7029 4357066.1685 E 01:353:43200 07:077:432004 ACOR 13434M0014 4594489.6779 -678367.7027 4357066.1652 E 07:077:43200 5 AIGL 10059M0011 4578299.9788 286538.9091 4418911.7911 E 02:252:00000

Each daily solution is transformed at epoch in the IGS05 reference frame using a 7 parameters Helmert transofrmation, and converted to ETRS89 using the appropriate conventional transformation formulaeETRS89 using the appropriate conventional transformation formulae (approach A)



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A monitoring approach (2/2)

For each station and solution, residuals are computed and l tt d ith t t li ti t d l it

Outliers are detected and corresponding solution is

plotted with respect to linear estimated velocity

Outliers are detected and corresponding solution is rejected.When a jump is detected on a station, a discontinuity is

t d i t d d f th fi l l tisetup and introduced for the final solution.Coordinates are propagated at minimum variance epochs.



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Time series residuals

Remark: the 0 horizontal axis corresponds to the position of theRemark: the 0 horizontal axis corresponds to the position of the station at minimum variance epoch



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The CATREF software



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Residuals analysis

RGP weekly solution : weighted RMS



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Final coordinates and velocities

• The reference epoch for the final coordinates delivery is p y2008.0

• For station with observation period shorter than 2 yearsFor station with observation period shorter than 2 years, reference coordinates are estimated at minimum variance epoch, and velocity using the ITRF2005 eurasian plate rotation model is used to transfer position at therotation model is used to transfer position at the reference epoch.

• F t ti ith b ti i d l th 2• For stations with observation period longer than 2 years, estimated velocities are used to transfer estimated position at the reference epoch.



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First results

• Comparison between IGS05 and ITRF2005 realizations has shown a difference of about 0.5 ppb for the network.

IGS05 is aligned with the ITRF2005 at a global level whereas we use a regional set of stations.

• Consistency at the cm level between the ETRF2000(R05)-F reference frame and the neighbouring countries ETRS89 realizationsrealizations



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ETRF2000(R05)-F velocities

Horizontal Vertical



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Grid model estimation by collocation method

Differences between ETRF2000(R05)-F and RGF93 reference frames can reach 4 cm

GRGP stations with coordinates available in the 2 frames



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Coordinates availability

For the RGP network, the following set of coordinates will , gbe published:

- for post-processing applications:for post processing applications:

IGS05 2008.0 coordinates and velocities

- for real-time positionning applications:

ETRF2000(R05) F di t f EPN t ti (EUREF IP)ETRF2000(R05)-F coordinates for EPN stations (EUREF-IP)legal RGF93 coordinates for the private RTK network stations



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Conclusions and coming actions

• Analysis refinement is still necessary.• From GPS week 1463 the network has been enlarged to a• From GPS week 1463, the network has been enlarged to a

global one including the IGS stations from the core network.• A global network reprocessing will be performed as soon as• A global network reprocessing will be performed as soon as

the IGS reprocessing files are available.• A cumulative weekly solution using CATREF software andA cumulative weekly solution using CATREF software and

the minimal constraint approach, expressed in IGS05 and in the ETRS89 realization using the Approach A formulae, will be maintained for each new solution.



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towards a new french etrs89 realization for the rgp krgp...

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